U.S. patent number 6,218,574 [Application Number 09/453,081] was granted by the patent office on 2001-04-17 for process for purifying long-chain dicarboxylic acid.
This patent grant is currently assigned to China Petrochemical Corporation, Fushun Research Institute of Petroleum & Petrochemical. Invention is credited to Dacheng Gao, Shuchen Liu, Jiangang Zhang.
United States Patent |
6,218,574 |
Liu , et al. |
April 17, 2001 |
Process for purifying long-chain dicarboxylic acid
Abstract
The present invention relates to an aqueous phase process for
purifying long-chain dicarboxylic acids from a liquid containing a
long-chain dicarboxylic acid/or a salt thereof. The invention
overcomes the disadvantages of low purity and high chroma of the
product obtained by using the aqueous phase process of the prior
art. Through the step of crystallizing the monosalt of long-chain
dicarboxylic acid, the present process reduces effectively the
content of such impurities as proteins and coloring materials in
the product and obtains the long-chain dicarboxylic acid product
having a total acid content of greater than 99 wt % and exhibiting
a white appearance.
Inventors: |
Liu; Shuchen (Fushun,
CN), Gao; Dacheng (Fushun, CN), Zhang;
Jiangang (Fushun, CN) |
Assignee: |
China Petrochemical Corporation
(Beijing, CN)
Fushun Research Institute of Petroleum & Petrochemical
(Fushun, CN)
|
Family
ID: |
5226965 |
Appl.
No.: |
09/453,081 |
Filed: |
December 2, 1999 |
Foreign Application Priority Data
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Dec 3, 1998 [CN] |
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98 1 21048.1 |
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Current U.S.
Class: |
562/593 |
Current CPC
Class: |
C07C
51/43 (20130101); C07C 51/43 (20130101); C07C
55/02 (20130101) |
Current International
Class: |
C07C
51/42 (20060101); C07C 51/43 (20060101); C07C
051/42 () |
Field of
Search: |
;562/593 |
Foreign Patent Documents
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56-26193 |
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Mar 1981 |
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JP |
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56-26194 |
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Mar 1981 |
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JP |
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Primary Examiner: Geist; Gary
Assistant Examiner: Calve; John N.
Attorney, Agent or Firm: Shanks & Herbert
Claims
What is claimed is:
1. A process for purifying long-chain dicarboxylic acids from a
liquid containing a long-chain dicarboxylic acid and/or a salt
thereof comprising the steps of:
a. adjusting the pH value of said liquid containing a long-chain
dicarboxylic acid and/or a salt thereof to 6.2-7.0 to form a
monosalt of long-chain dicarboxylic acid;
b. dissolving the monosalt of long-chain dicarboxylic acid by
heating to obtain a solution containing the monosalt of long-chain
dicarboxylic acid;
c. crystallizing the solution obtained in step b by cooling, and
filtering the solution to obtain a filter cake of the monosalt of
long-chain dicarboxylic acid and a filtrate;
d. dissolving the filter cake of the monosalt of long-chain
dicarboxylic acid obtained in step c by heating;
e. converting the monosalt of long-chain acid into long-chain
dicarboxylic acid; and
f. isolating the long-chain dicarboxylic acid.
2. The process according to claim 1, wherein in step a said pH
value is adjusted to 6.5-6.8.
3. The process according to claim 1, wherein said long-chain
dicarboxylic acid is a C.sub.10 -C.sub.18 long-chain dicarboxylic
acid or a mixture of C.sub.10 -C.sub.18 long-chain dicarboxylic
acids.
4. The process according to claim 1, wherein the filtrate obtained
in step III is treated with an adsorbent, and the treated filtrate
is used for dissolving the filter cake in step d.
5. The process according to claim 1, wherein said liquid containing
a long-chain dicarboxylic acid and/or a salt thereof is a
fermentation liquid containing mycelia of an n-alkane.
6. The process according to claim 5, wherein prior to step a the
mycelia are removed from the fermentation liquid and wherein in
step a the pH value is adjusted with an acid to 6.2-7.0.
7. The process according to claim 1, wherein in step e the monosalt
of long-chain dicarboxylic acid is converted into long-chain
dicarboxylic acid by acidifying with an acid.
8. The process according to claim 5, wherein prior to step a the
fermentation liquid is acidified directly and is filtered to obtain
a filter cake of long-chain dicarboxylic acid containing mycelia,
and an alkali solution is added to the filter cake.
9. The process according to claim 8, wherein in step e the monosalt
of long-chain dicarboxylic acid is converted into long-chain
dicarboxylic acid by the following steps:
i). adding an alkali to form completely a solution of disalt of
long-chain dicarboxylic acid;
ii). filtering off the solids; and
iii). acidifying the filtrate obtained in the above step to convert
the disalt of long-chain dicarboxylic acid into long-chain
dicarboxylic acid completely.
10. The process according to claim 8, wherein prior to step c the
solution obtained in step b is filtered to obtain a filtrate
containing monosalt of long-chain dicarboxylic acid and the
filtrate is subjected to the crystallization of step c.
Description
The present invention relates to a process for purifying long-chain
dicarboxylic acid, more particularly, a process for purifying
long-chain dicarboxylic acid from a liquid containing a long-chain
dicarboxylic acid and/or a salt thereof.
Long-chain dicarboxylic acid is a metabolic product obtainable from
the fermentation of n-alkane by microorganisms. The fermentation
liquid is a complex multi-phase system which contains unreacted
n-alkane, cells of microorganisms and fragments thereof, unutilized
culture medium and metabolites, secretion substances of the
microorganism and the like, especially in which a large amount of
impurities, such as proteins and coloring materials, will have
serious adverse effect on the purity and appearance of the
product.
At present, the process for purifying the long-chain dicarboxylic
acid is typically classified into two types: a solvent process and
an aqueous phase process. Though the problems mentioned above can
be solved by using the solvent process, its application is
significantly restricted by the problems such as high investment,
residual alkane and solvent in the product, safety of production
and so on. The aqueous phase process can overcome the defects that
the solvent process has, but the purity and color appearance of its
product cannot attain to a higher level. For example, JP56026193
and JP56026194 disclose an aqueous phase process for separating
dicarboxylic acid, wherein the operation steps comprise alkalifying
and stewing the end fermentation liquid, centrifuging to remove
mycelia, adding siliceous earth to adsorb unreacted reactants and
by-products, then filtering, acidifying and crystallizing the
filtrate. Finally, the product of dicarboxylic acid is obtained
after filtration and drying. The main problem existing in the
processes mentioned above is the autolysis of cells during
alkalifying and stewing, thereby the impurities such as proteins
and coloring materials in cells are dissolved into the fermentation
liquid, consequently the purity of total dicarboxylic acid product
is only 98.5% at highest, and the coloring materials in the product
are difficult to be removed. The product is then light tawny in
appearance.
The object of the present invention is to provide an aqueous phase
process for purifying long-chain dicarboxylic acid from a liquid
containing a long-chain dicarboxylic acid and/or a salt thereof so
as to improve the purity of product, decrease the chroma of product
and provide the product with higher quality.
Directing to the defects existing in the prior art, the present
invention further purifies long-chain dicarboxylic acid product by
using crystallization of monosalt of long-chain dicarboxylic acid.
It has been found upon research that the monosalt of long-chain
dicarboxylic acid has very weak ability to adsorb the coloring
materials. Consequently, during crystallization of monosalt of the
long-chain dicarboxylic acid, the soluble proteins and coloring
materials remain in the mother liquid when the monosalt of
long-chain dicarboxylic acid is filtered. So this process has a
dual function of removing both proteins and coloring materials,
thus the purity of the long-chain dicarboxylic acid product is
improved and the chroma of the product decreases.
Thus the present invention provides a process for purifying
long-chain dicarboxylic acid from a liquid containing a long-chain
dicarboxylic acid and/or a salt thereof comprising the steps
of:
I. adjusting the pH value of said liquid containing a long-chain
dicarboxylic acid and/or a salt thereof to6.2-7.0 to form a
monosalt of long-chain dicarboxylic acid;
II. dissolving the monosalt of long-chain dicarboxylic acid by
heating to obtain a solution containing the monosalt of long-chain
dicarboxylic acid;
III. crystallizing the solution obtained from the above step by
cooling, and filtering the solution to obtain a filter cake of the
monosalt of long-chain dicarboxylic acid and a filtrate;
IV. dissolving the filter cake of the monosalt of long-chain
dicarboxylic acid obtained in the above step by heating;
V. converting the monosalt of long-chain acid into long-chain
dicarboxylic acid; and
VI isolating the long-chain dicarboxylic acid.
The present invention is suitable for use with any liquid that
contains a long-chain dicarboxylic acid and/or a salt thereof. An
example of such a liquid is the fermentation liquid obtained
through fermentation of an n-alkane by microorganisms.
The present invention applies to any long-chain dicarboxylic acid.
Preferably, the long-chain dicarboxylic acid may be a C.sub.10
-C.sub.18 long-chain dicarboxylic acid or a mixture of C.sub.10
-C.sub.18 long-chain dicarboxylic acids.
The present invention utilizes a distinct property of the monosalt
of long-chain dicarboxylic acid, that is, its weak ability to
adsorb the coloring materials. So it is important to properly
adjust the pH value of the liquid so as to ensure that the
dicarboxylic acid is converted into its monosalt form completely.
Suitable pH value is from 6.2 to 7.0, preferably from 6.5 to 6.8.
Acids and bases used to adjust the pH value are those which are
commonly used in the art for this purpose, including organic and
inorganic acids and bases. Examples of such acids are sulfuric
acid, nitric acid, hydrochloric acid and phosphoric acid. Examples
of such bases are alkali metal hydroxides, such as sodium hydroxide
and potassium hydroxide.
Where the liquid from which the long-chain dicarboxylic acid to be
purified is a fermentation liquid of an n-alkane, said liquid is
advantageously treated by conventional method to remove the mycelia
which may be present in the liquid prior to being processed by the
process of the present invention. The treated liquid may be
adjusted with an acid to 6.2-7.0. Alternatively, said fermentation
liquid may be acidified directly, for example to a pH value of
2.0-4.0, preferably with heating, without removal of the mycelia.
This may cause some of the proteins in the fermentation liquid to
be denatured and precipitated. Then, the acidified liquid may be
filtered to obtain a filter cake of long-chain dicarboxylic acid
containing mycelia, leaving soluble proteins and part of the
coloring materials in the filtrate. Optionally, alkanes remaining
in the fermentation liquid may be separated from the liquid before
the filtration is carried out. An alkali solution is added to the
filter cake to obtain a liquid that is now ready to be processed by
the process of the present invention.
After the dicarboxylic acid is converted into its monosalt form by
pH adjustment, said liquid is heated by conventional means to
dissolve the monosalt of the dicarboxylic acid. The solution
obtained is cooled such that the monosalt of dicarboxylic acid is
crystallized from the solution. Alternatively, the solution
containing the monosalt of long-chain dicarboxylic acid is filtered
to remove solids prior to being crystallized.
After crystallization, the solution is filtered to obtain a filter
cake of the monosalt of dicarboxylic acid and a filtrate. The
filter cake obtained is dissolved in an aqueous solvent (for
example, water), preferably with heating. The filtrate obtained may
be treated with an adsorbent to remove coloring materials and
soluble proteins. The treated filtrate may be used for dissolving
the filter cake mentioned above. Said adsorbent is selected from
conventional adsorbents which are suitable for the removal of
coloring materials and soluble proteins, for example, active carbon
and active clay. The amount of the adsorbent added may be 0.5-3% by
weight based on the weight of the filtrate and the treatment with
the adsorbent may be carried out at 20-60.degree. C. for 15-30
minutes.
After the filter cake of the monosalt of dicarboxylic acid is
completely dissolved, the monosalt of dicarboxylic acid is
converted to its acid form by any of conventional methods. For
example, the monosalt may be acidified with an acid to a pH value
of 2.0-4.0, preferably with heating to 80-95.degree. C.
Alternatively, where a fermentation liquid is acidified directly
prior to being processed by the process of the present invention,
the monosalt of the dicarboxylic acid may be converted to its acid
form by the following steps:
a). adding an alkali to form completely a solution of disalt of
long-chain dicarboxylic acid;
b). filtering off the solids; and
c). acidifying the filtrate obtained in the above step to convert
the disalt of long-chain dicarboxylic acid into long-chain
dicarboxylic acid completely.
The last step of the present invention is to isolate the long-chain
dicarboxylic acid. In this connection, conventional methods that
are well known in the art may be used, for example,
crystallization, filtration, washing, drying and so on.
In an embodiment of the invention, the following procedures may be
followed:
1. Adding an acid to the filtrate, which is obtained after an end
fermentation liquid of an n-alkane is filtered and mycelia are
removed, to adjust its pH value to 6.2-7.0, then heating it to
85-100.degree. C. to dissolve completely the formed monosalt of
long-chain dicarboxylic acid, and subsequently reducing the
temperature to 75-85.degree. C. and maintaining the temperature for
15-30 minutes.
2. Cooling the resultant solution to room temperature, and
filtering to obtain a filter cake of the monosalt of long-chain
dicarboxylic acid and a filtrate.
3. dissolving the monosalt of long-chain dicarboxylic acid and
adding an acid to the resultant solution to adjust its pH value to
2.0-4.0, and heating the solution to 80-95.degree. C. to convert
the monosalt of long-chain dicarboxylic acid into the long-chain
dicarboxylic acid completely, then reducing the temperature to
70-85.degree. C., and maintaining the temperature for 15-30
minutes.
4. Cooling and crystallizing the solution obtained in step 3, and
obtaining a purified product of the long-chain dicarboxylic acid
through the steps of filtering, washing and drying and so on.
Wherein the pH value of the solution acidified in step 1 is
controlled preferably in the range of 6.5-6.8. 0.5-3 Wt % of an
adsorbent can be added to the filtrate obtained in step 2 to remove
coloring materials and soluble proteins. The adsorption treatment
is carried out at 20-60.degree. C. for 15-30 minutes. Then the
mixture is filtered to obtain the filtrate decolorized and
deproteinized. The resultant filtrate is used for dissolving the
filter cake in step 3.
In another embodiment of the invention, the following procedures
may be followed:
1. Acidifying directly an end fermentation liquid of an n-alkane,
adjusting the pH value of the resultant solution to 2-4, then
heating it to 75-90.degree. C., separating and recovering alkane at
a standstill, then reducing slowly the temperature to room
temperature, and filtering to obtain a filter cake of long-chain
dicarboxylic acid containing mycelia.
2. Mixing the filter cake of long-chain dicarboxylic acid
containing mycelia with water, adding an alkali to the resultant
mixture to adjust its pH value to 6.2-7.0, then heating to
85-100.degree. C. to dissolve completely the formed monosalt of
long-chain dicarboxylic acid, and reducing the temperature of the
resultant solution to 75-85.degree. C. and maintaining the
temperature for 15-30 minutes.
3. Reducing slowly the temperature of the solution obtained in step
2 to room temperature in order to promote the crystallization of
the monosalt of long-chain dicarboxylic acid, and filtering to
obtain a filter cake of the monosalt of long-chain dicarboxylic
acid containing mycelia and a filtrate.
4. Dissolving the filter cake obtained in step 3, adding an alkali
solution to adjust its pH value to 9-12, then heating it slowly to
50-70.degree. C. to form completely a solution of the disalt of
long-chain dicarboxylic acid, and filtering to obtain a clarified
filtrate of the disalt of long-chain dicarboxylic acid.
5. Acidifying the clarified filtrate of the disalt of long-chain
dicarboxylic acid obtained in step 4 by adding an acid, adjusting
its pH value to 2-4, and heating it to 75-95.degree. C. to convert
the disalt of long-chain dicarboxylic acid into long-chain
dicarboxylic acid completely, thereafter decreasing the temperature
to 70-85.degree. C. and maintaining the temperature for 15-30
minutes, and then cooling slowly to room temperature, and obtaining
a purified long-chain dicarboxylic acid product through the steps
of filtering, washing and drying.
Wherein the filtrate obtained in step 3 may be treated with 0.5-3
wt % of an adsorbent at 20-60.degree. C. for 15-30 minutes, and
filtered to obtain a clarified filtrate which is then used for
dissolving the filter cake in step 4. In step 4, in order to reduce
the filtration time, 1-3 wt % of a filter aid may be added to the
solution and mixed thoroughly prior to filtration.
In still another embodiment of the invention, the following
procedures may be followed:
1. Acidifying directly an end fermentation liquid of an n-alkane to
adjust its pH value to 2-4, heating to 75-90.degree. C., separating
and recovering alkane at a standstill, then reducing slowly the
temperature to room temperature, and filtering slowly the
temperature to room temperature, and filtering to obtain a filter
cake of long-chain dicarboxylic acid containing mycelia.
2. Mixing the filter cake of the long-chain dicarboxylic acid
containing mycelia with water, wadding an alkali to adjust its pH
value to 6.2-7.0, then heating to 85-100.degree. C. to dissolve
completely the formed monosalt of long-chain dicarboxylic acid.
3. Filtering the solution obtained in step 2 to obtain a filtrate
containing the monosalt of long-chain dicarboxylic acid.
4. Maintaining the temperature of the filtrate obtained in step 3
at 75-85.degree. C. for 15-3 minutes, then reducing the temperature
slowly to room temperature to crystallize the monosalt of
long-chain dicarboxylic acid, and filtering to obtain a filter cake
of the monosalt of long-chain dicarboxylic acid and a filtrate.
5. Dissolving the filter cake obtained in step 4 and adding an acid
to adjust the pH value to 2.0-4.0, and heating to 80-95.degree. C.
to convert the monosalt of long-chain dicarboxylic acid into the
long-chain dicarboxylic acid completely, then reducing the
temperature to 70-85.degree. C. and maintaining this temperature
for 15-30 minutes, then cooling and crystallizing, and obtaining a
purified product of long-chain dicarboxylic acid through the steps
of filtering, washing, drying and so on.
Wherein the filtrate obtained in step 4 may be treated with 0.5-3
wt % of an adsorbent at 20-60.degree. C. for 15-30 minutes, and
filtered to obtain a clarified filtrate which is then used for
dissolving the filter cake in step 5. In step 3, in order to reduce
the filtration time, 1-3 wt % of a filter aid may be added to the
solution and mixed thoroughly prior to filtration.
The acid used for acidification as mentioned above according to the
invention may be H.sub.2 SO.sub.4, HNO.sub.3, HCl or H.sub.3
PO.sub.4, and the alkali used may be an alkali metal hydroxide,
such as NaOH, KOH and the like. The adsorbent used may be active
carbon or active clay, and the filter aid used may be siliceous
earth.
In the process according to the present invention, when the
monosalt of long-chain dicarboxylic acid is to be crystallized and
when the final acidification and crystallization is to be carried
out to obtain the purified dicarboxylic acid, it is preferable that
the temperature be controlled and maintained at 75-85.degree. C.
for 15-30 minutes, and then reduced slowly to promote the crystal
growth. This facilitates not only the operation of filtration, but
also retention of coloring materials and soluble proteins in the
filtrate. In addition, since the monosalt of long-chain
dicarboxylic acid has very weak ability to adsorb coloring
materials and proteins, the proteins and coloring materials remain
in the filtrate when the monosalt of the long-chain dicarboxylic
acid is crystallized and filtered, so that the proteins and
coloring materials can be removed by adding an adsorbent into the
filtrate. The long-chain dicarboxylic acid prepared according to
the process of the present invention has a total acid purity of
higher than 99 wt %, a nitrogen content of less than 50 .mu.g/g, a
yield of greater than 90 wt %, a chroma of less than 40, and the
product exhibits a white appearance. The long-chain dicarboxylic
acid prepared according to the process of the present invention can
be widely used for synthesizing such products as high-grade perfume
and advanced thermosol and so on.
The present invention will be illustrated by the following
examples.
EXAMPLE 1
200 Ml of a fermentation liquid having a concentration of 124 g/l
of C.sub.10 dicarboxylic acid and a pH value of 7.9, which had been
fermented with candida tropicalis, was treated for removal of
mycelia. 3 Mol/l of H.sub.2 SO.sub.4 was added thereto to adjust
its pH value to 6.5. The mixture was then heated to 93.degree. C.,
thereafter the temperature was reduced to and maintained at
80.degree. C. for 30 minutes, and then reduced slowly to room
temperature. After filtration, a filter cake of the monosodium salt
of dicarboxylic acid and a filtrate were obtained.
1 Wt % of active carbon powder was added to the filtrate and the
filtrate was treated for adsorption at 40.degree. C. for 30
minutes, then filtered again to obtain another filtrate, which was
then mixed with the above filter cake by adding 150 ml of water. To
the resultant mixture was added 3 mol/l of H.sub.2 SO.sub.4 to
adjust the pH value to 3.0, then heated to 80.degree. C. and
stirred throroughly, and subsequently cooled at a standstill to
room temperature, filtered, washed and dried to obtain a purified
C.sub.10 dicarboxylic acid product. The properties of the product
are shown in Table 1.
EXAMPLE 2
To 200 ml of a fermentation liquid having a concentration of 130
g/l of C.sub.13 dicarboxylic acid and a pH value of 7.6, which had
been fermented with candida tropicalis, was added 3 mol/l of
H.sub.2 SO.sub.4 to adjust its pH value to 4.0, heated to
80.degree. C. and placed at a standstill for 30 minutes. Then the
alkane remaining in the solution was removed, and the temperature
of the solution was reduced to room temperature. After filtration
and washing, a crude filter cake of C.sub.13 dicarboxylic acid
containing mycelia was obtained.
The crude filter cake was blended with 325 ml of water. To the
resultant mixture was added 10 mol/l of NaOH solution to adjust its
pH value to 6.5, and heated to 95.degree. C., then cooled to and
maintained at 80.degree. C. for 30 minutes, and then cooled slowly
to room temperature. After filtration, a filter cake of the
monosodium salt of C.sub.13 dicarboxylic acid and a filtrate were
obtained. 1 Wt % of active carbon powder was added to the filtrate
and the filtrate was treated for adsorption at 40.degree. C. for 30
minutes. The filtrate obtained by the filtration was mixed with the
filter cake of the monosodium salt of C.sub.13 dicarboxylic acid.
10 Mol/l of NaOH was added to adjust the pH value to 10.2. The
resultant mixture was heated to 60.degree. C. to form the disodium
salt of C.sub.13 dicarboxylic acid. Then 2 wt % of siliceous earth
was added as a filter aid and mixed thoroughly. After filtering off
solids, a filtrate was obtained. Subsequently 3 mol/l of H.sub.2
SO.sub.4 was added to the filtrate to adjust its pH value to 4.0.
after heating to 80.degree. C. and cooling at a standstill to room
temperature, C.sub.13 dicarboxylic acid was obtained which was then
filtered, washed and dried to obtain a purified C.sub.13
dicarboxylic acid product. The properties of the product are shown
in Table 1.
EXAMPLE 3
200 Ml of a fermentation liquid having a concentration of 130 g/l
of C.sub.13 dicarboxylic acid and a pH value of 7.6 was treated for
removal of mycelia. 3 Mol/l of H.sub.2 SO.sub.4 was added thereto
to adjust its pH value to 6.2, then heated to 95.degree. C.,
thereafter the temperature was reduced to and maintained at
80.degree. C. for 30 minutes, and then reduced slowly to room
temperature. After filtration, a filter cake of the monosalt of
C.sub.13 dicarboxylic acid and a filtrate were obtained.
1 Wt % of active carbon powder was added to the filtrate and the
filtrate was treated for adsorption at 40.degree. C. for 30
minutes, then filtered again to obtain another filtrate, which was
then mixed with the above filter cake by adding 150 ml of water. To
the resultant mixture was added 3 mol/l of H.sub.2 SO.sub.4 to
adjust its pH value to 3.2, then heated to 80.degree. C. and mixed
thoroughly, and subsequently cooled at a standstill to room
temperature. After filtration, washing and drying, a purified
C.sub.13 dicarboxylic acid product was obtained. The properties of
the product are shown in Table 1.
EXAMPLE 4
To 200 ml of a fermentation liquid having a concentration of 120
g/l of the mixed dicarboxylic acids of C.sub.13 and C.sub.14 and a
pH value of 7.6, which had been fermented with candida tropicalis,
was added 3 mol/l of H.sub.2 SO.sub.4 to adjust its pH value to
3.4, then heated to 80.degree. C. at a standstill for 30 minutes.
The C.sub.13 and C.sub.14 alkanes remaining in the solution were
removed, then the resultant solution was cooled to room
temperature. After filtration and washing, a filter cake of mixed
dicarboxylic acids containing mycelia was obtained.
200 Ml of water was added to the filter cake and mixed thoroughly.
To the resultant mixture was added 10 mol/l of NaOH to adjust its
pH value to 6.6, and heated to 95.degree. C., then cooled to and
maintained at 80.degree. C. for 30 minutes, subsequently, cooled
slowly to room temperature. After filtration, a filter cake of the
monosodium salt of mixed long-chain dicarboxylic acids and a
filtrate were obtained. 1 Wt % of active carbon powder was added to
the filtrate and the filtrate was treated for adsorption at
40.degree. C. for 30 minutes. The filtrate was filtered again to
obtain another filtrate that was then mixed with the above filter
cake. To the resultant mixture was added 10 mol/l of NaOH to adjust
its pH value to 9.7, and heated to 60.degree. C., then 2 wt % of
siliceous earth was added and stirred thoroughly. The solids were
filtered off. 3 Mol/l of H.sub.2 SO.sub.4 was added to the filtrate
to adjust its pH value to 3.0, then heated to 80.degree. C., and
subsequently cooled at a standstill to room temperature. After
filtration, washing and drying, a purified mixed long-chain
dicarboxylic acid product was obtained. The properties of the
product are shown in Table 1.
EXAMPLE 5
To 400 ml of a fermentation liquid having a concentration of 130
g/l C.sub.13 dicarboxylic acid and a pH value of 7.5, which had
been fermented with candida tropicalis, was added 3 mol/l of
H.sub.2 SO.sub.4 to adjust its pH value to 4.0, then heated to
80.degree. C. and placed at a standstill for 30 minutes. Then the
alkane remaining in the solution was separated, and the temperature
of the solution was reduced to room temperature. After filtration
and washing, a crude filter cake of C.sub.13 dicarboxylic acid
containing mycelia was obtained.
The crude filter cake of C.sub.3 dicarboxylic acid was mixed with
650 ml of water. To the resultant mixture was added 10 mol/l of
NaOH to adjust its pH value to 6.6, and heated to 96.degree. C. to
dissolve completely the monosodium salt of C.sub.13 dicarboxylic
acid. Then the solids were filtered off. The filtrate was cooled to
80.degree. C. and maintained at the temperature for 20 minutes,
then cooled slowly to room temperature, and filtered to obtain a
filter cake of monosodium salt of C.sub.13 dicarboxylic acid and a
filtrate. 1.8 Wt % of active carbon powder was added to the
filtrate and the filtrate was treated for adsorption at 50.degree.
C. for 20 minutes. The filtrate was filtered again to obtain
another filtrate that was then mixed with the filter cake of the
monosodium salt of C.sub.13 dicarboxylic acid. 3 Mol/l of H.sub.2
SO.sub.4 was added to the resultant mixture to adjust its pH value
to 4.0 thereby forming the C.sub.13 dicarboxylic acid completely,
heated to 80.degree. C., and cooled at a standstill to room
temperature. After filtration, washing and drying, a purified
C.sub.13 dicarboxylic acid product was obtained. The properties of
the product are shown in Table 1.
EXAMPLE 6
To 200 ml of a fermentation liquid having a concentration of 35 g/l
of C18 dicarboxylic acid and a pH value of 8.2, which had been
fermented with candida tropicalis, was added 3 mol/l of H.sub.2
SO.sub.4 to adjust its pH value to 3.0,heated to 90.degree. C. and
placed at a standstill for 30 minutes. Then the alkane remaining in
the solution was separated. The solution was cooled down to room
temperature. After filtration and washing, a filter cake of
C.sub.18 dicarboxylic acid containing mycelia was obtained.
130 Ml of water was added to the filter cake and mixed thoroughly.
To the resultant mixture was added 10 mol/l of NaOH to adjust its
pH value to 7.0, and heated to 95.degree. C., then the temperature
was reduced to and maintained at 80.degree. C. for 30 minutes, and
thereafter cooled slowly to room temperature. After filtration a
filter cake of monosodium salt of dicarboxylic acid and a filtrate
was obtained. 1 Wt % of active carbon powder was added to the
filtrate and the filtrate was treated for adsorption at 40.degree.
C. for 30 minutes. Then the filtrate was filtered again to obtain
another filtrate that was then mixed with the above filter cake. To
the resultant mixture was added 10 mol/l of NaOH to adjust its pH
value to 10.7 and heated to 60.degree. C. Then 2 wt % of siliceous
earth was added and mixed thoroughly. Solids were filtered off. To
the clarified filtrate was added 3 mol/l of H.sub.2 SO.sub.4 to
adjust its pH value to 3.0, heated to 80.degree. C. and cooled to
room temperature at a standstill. After filtration, washing and
drying, a purified C.sub.18 dicarboxylic acid product was obtained.
The properties of the product are shown in Table 1.
TABLE 1 Properties of the product obtained according to the present
invention Yield of Content Alkane Nitro- pro- Appear- of total
Content content gen duct ance acid of in content (wt of Ex. No. (wt
%) diacid product Chroma (.mu.g/g) %) product Exam- 99.17 97.93
unde- 24 24.7 90.8 white ple 1 (C.sub.10) tectable Exam- 99.1 98.2
unde- 32 23.2 90.3 white ple 2 (C.sub.13) tectable Exam- 99.35 98.7
unde- 28.5 34.2 93.2 white ple 3 (C.sub.13) tectable Exam- 99.4 /
unde- 25.3 29.8 92.5 white ple 4 tectable Exam- 99.2 98.3 unde- 31
22.8 90.2 white ple 5 (C.sub.13) tectable Exam- 98.55 96.16 unde-
34 29.2 90.2 white ple 6 (C.sub.18) tectable
In table 1, total acid was determined by titrimetry, dicarboxylic
acid was determined by gas chromatography using an internal
standard, alkane was determined by gas chromatography, chroma was
measured by platinum-cobalt colorimetry at dicarboxylic acid
concentration of 20 g/l, and nitrogen is determined by
chemiluminescence (total nitrogen).
* * * * *